Abstract:

This study was conducted using In Vitro gas production techniques in order to evaluate fermentative nutrition characteristics of supplementary concentrate mixed with native pastures in Qinghai plateau. The supplementary concentrate combined with Kobresia pygmaea Charke-Stipa aliena Keng, Kobresia pygmaea Charke, Gramineae, Kobresia pygmaea Charke at the ratios of 25:75, 50:50, and 75:25, respectively. The results showed that all of four combinations increased accumulative gas production, the maximum theoretical gas production and gas producing velocity, and decreased gas lag time, which were available for rumen degradation and pasture utilization. The pH values of all combinations during fermentation In Vitro were in normal ranges, the digestibility of organic matter and concentration of volatile fatty acids (acetate and propionate) were improved significantly, and the ratios of acetate to propionate were low. With the levels of supplementary concentrate increasing, the positive associate effects enhanced and reached the highest values at the 75% proportion of supplementary concentrate. Therefore, this study suggested that the ratio of 75:25 was the best combination of supplementary concentrate with pasture, which provided scientific basis of nutritional balance supplement for cold-season grazing yaks in the Yushu district of three-river source area of Qinghai province.

Key words: Yak, Native pasture, Supplementary concentrate, Combined fermentation, Nutritional characteristic, In Vitro gas production technique

摘要：

本研究采用体外产气法评价了青海高原牦牛精补料分别与高山嵩草-异针茅(Kobresia pygmaea Charke-Stipa aliena Keng)、高山嵩草(Kobresia pygmaea Charke)、紫花针茅(Gramineae)、高山嵩草+杂类(Kobresia pygmaea Charke and others)4种草地型冷季天然牧草均按25:75,50:50,75:25的比例两两组合后的发酵营养特性。结果表明,精补料分别与4种牧草组合均能有效提高牧草发酵的累计产气量、理论最大产气量和产气速率常数,降低产气延滞时间,有利于牧草在瘤胃中的降解利用;同时,两两组合后体外发酵pH值均处于正常变化范围内,体外有机物质消化率及挥发型脂肪酸(乙、丙酸)浓度明显提高,而乙丙酸比降低,此正组合效应随精补料添加水平升高而逐渐增强,即精补料75%比例的组合均为最高,且添加精补料还表现出能减少牧草体外发酵甲烷产生量的潜在趋势。综合研究结果确定了精补料与4种草地型牧草均以75:25的比例组合搭配效果更优,为青海高原三江源玉树地区放牧牦牛冷季营养平衡补饲提供了科学依据。

关键词: 牦牛, 天然牧草, 精补料, 组合发酵, 营养特性, 体外产气法